Ensuring tight computational security against higher-order DPA attacks

While DES has been proven to be breakable within a day given sufficient computational power, AES is still in use because it is extremely resistant to cryptanalytic attacks. Power Analytic Attacks use power consumption traces of the hardware or software implementation of these algorithms to reduce search space exponentially in the size of the key, thereby making computational complexity several orders of magnitude lower. This paper analyzes the increase in the computational advantage of an adversary who uses DPA and higher order power analysis attacks as opposed to algorithmic cryptanalysis. We highlight why there can be no perfect masking against DPA, and then define a standard for the security of masking countermeasures to such attacks. The main contribution is a security metric for systems and a cut-off for the number of encryptions allowable for a given order of masking to make the system immune to higher order DPA attacks.